1. Field of the Invention
The present invention relates to methods for designing the sole shape of golf club irons, and systems for the same.
2. Description of Related Art
There are many parameters to the shape of a golf club head. Club heads generally include a face portion, a top line portion (in iron heads; wood heads have a crown portion), a side portion, a sole portion, and a toe portion, and are joined to a shaft. A golf club's performance changes based not only on the size of those portions, but also on the lie angle between the shaft and the ground when looking at the club head from the face side, the loft angle between the shaft axis and the face surface when looking at the club head from the toe side, the face angle of the face surface with respect to the shaft axis when looking at the club head from above, and the relationship between the largest deflection position of the face surface and the position of the center of gravity of the head unit itself that is projected onto the face surface. The material of the club head and the shaft design also have an impact on club performance.
In the case of an iron, its sole portion forcefully strikes the ground. The shape of the sole is also a crucial element in minimizing head shake without reducing head speed. As shown in FIG. 6, the shape of the sole may be bounce, scoop, round, or flat, and each of these shapes is designed to fit the function that is expected of that club, such as making balls easier to hit up, improving the swing-though release, and increasing head stability during impact. The sole portion also may be provided with a groove or some other types of patterns. When the shaft axis is positioned vertical to the ground, viewed from the toe side, the sole surface opens up toward the front of the club in the bounce sole and toward the rear in the scoop sole. The overall shape of the bounce sole or the scoop sole is defined by the bounce angle (a) or the scoop angle (b) between the ground and the sole surface respectively. Round soles have a curved sole surface and cannot be defined by the bounce or scoop angle. Flat soles are designed so that their sole surface is parallel to the ground, and have bounce and scoop angles of 0°. Other important parameters include the weight distribution within the iron head, the width of the sole surface, and, in the case of round soles, the radius of curvature of the sole surface.
There are thus many types of sole shapes, and in designing those shapes there is a need to more quantitatively evaluate the effects of the sole shape. Further, each person has their own unique golf swing. Although a sole design that matches the characteristics of a player's golf swing is preferable, the choice of solve designs is currently made based on instinct. If it is possible to systematically arrive at the shape or parameter values of an ideal sole, then sets of irons that include different sole shapes may be provided for different players.
It should be noted that the method presented in JP 2005-6763A is known as one method for creating prototype golf club heads and then evaluating those heads.